Composite material based on organic fibers for thermally mouldable shoe components

ABSTRACT

The invention relates to a composite material for thermally formable shoe components on an organic fiber base containing an organic fiber material or a mixture of two or more organic fiber materials and a binding agent consisting of a thermoplastic polymer or a mixture of two or more thermoplastic polymers and natural latex. The invention also relates to a process for producing such a thermoplastic composite material and to the providing of a thermally activatable adhesive in the flow transition range of the composite material.

This is a continuation of International Application PCT/EP2004/008697, filed Aug. 3, 2004, which claims priority to German Application No. 103 36 509.5, filed Aug. 8, 2003, the disclosures of each are hereby incorporated by reference in its entirety.

The invention relates to a composite material for thermally formable shoe components containing fiber materials, a thermoplastic binding agent and natural latex. Furthermore, the invention relates to a process for producing such a composite material for thermally formable shoe components on an organic fiber basis. A coating of the composite material with adhesive used to bind the composite material for thermally formable shoe components during processing in the manufacture of shoes is also subject matter of the invention.

Composite materials, also called composites, are materials produced by the incorporation of a base material, present, e.g., in the form of fibers, into a second substance (the matrix). Certain properties (e.g., mechanical properties, surface properties or certain behavior under external influences) of the incorporated substance are used in this instance for the composite material. The base material can vary greatly in its proportion of ingredients relative to the matrix surrounding it. Thus, the matrix component in wooden materials, to which, e.g., the known pressboard plates belong, is as a rule only 10-15%. In contrast thereto, the matrix component in fiber-reinforced plastics, e.g., in plastics reinforced with glass fibers, can be significantly greater, approximately over 70 or 80%.

It is frequently possible to impart certain properties of the base material to the composite by a suitable selection of base material and matrix, which properties are paired with certain properties of the matrix. Thus, e.g., the use of glass- or natural-substance fibers in duromer plastics can bring about a transfer of the tensile strength of the fibers to the plastic matrix, which for its part contributes advantages of shaping, form stability and workability to the composite.

The production of composites is frequently used to produce a material from byproducts accumulating during the processing of a certain base material with characteristic properties of the base material. The corresponding composite material can then be used as a rule at least as replacement material for the base material and thus permits a “substance-related” utilization of the waste and/or byproducts of the base material. This is the case, e.g., in the utilization of wood waste in pressboard plates. A further example for a substance-related utilization of byproducts is the processing of cutting and stamping remnants in the production of leather and shoes to leather fiber materials.

Leather remnants can be defibered and then processed to leather fiber materials (LEFA). LEFA are as a rule single-layer areal structure consisting of leather fibers and binding agents. LEFA plates have been used in the shoe industry since the end of the thirties already, e.g., for producing heel caps, toe caps, insoles and midsoles, outer soles, welts and heels.

Properties such as flexibility and durability qualify leather for use in the shoe industry or purse maker industry. However, since leather has no thermoplastic properties it can only be used to a limited extent for thermally formable shoe components. It was also not possible previously to fit out leather-like replacement materials, e.g., LEFA, in such a manner that they on the one hand have the thermoplastic properties necessary for use in the shoe industry, in particular for thermally deformable, high-quality heel caps and toe caps as well as outer soles, and on the other hand nevertheless have leather-like properties. The deformability of the LEFA heel and toe caps was to date achieved as a rule in a traditional, work-intensive process. The LEFA cap material is briefly soaked in water, stamped out after 24 hours, skived, mechanically hot-deformed under pressure, coated with dispersion, dried and sent packed in foil for further processing in the production of shoes.

On the other hand, thermal deformability in a rational process offers synthetic heel and toe cap materials consisting of thermoplastically deformable material based on plastic that are reinforced by a textile fabric. The processing can take place in accordance with the hot-cold process. In it, the stamped-out and only slightly sharpened cap is thermally activated by heating with infrared light, that is, heated to a temperature above the flow transition boundary, formed above an ice-cooled form and sent to further processing in the production of shoes. Alternatively, the cap material can also be supplied plane without pre-forming. The actual, accurately-fitting deformation takes place in both processes in the shoe factory by thermal activation, that is, heating to a temperature above the flow transition boundary on the last. The adhering of the cap to the lining material and the upper material also takes place during this time, since the thermally activatable adhesive is contained in the synthetic cap material and the thermal activation of the adhesive takes place in the temperature range above the flow transition boundary of the synthetic cap material.

LEFA caps are used with preference in high-quality shoes on account of their leather-like properties. Synthetic caps are processed primarily in economical shoes produced in great numbers on account of their high mechanical workability.

The use of leather substitute material in shoe components places special demands on the material used. Thus, the material must have certain elastic properties, in particular a sufficient base- and long-lasting elasticity. In addition, the material must have sufficient resistance to mechanical stresses, in particular to becoming brittle when cold.

The present invention therefore had the task of making a composite available that largely has the properties of high-quality LEFA buffer materials and on the other hand is suitable for processing in modem processes as in the use of synthetic heel- and toe cap materials and, in addition, can be processed in an even more rational manner.

In the context of the a preferred embodiment of the invention, it was further a task to provide the composite material with a thermally activatable adhesive with which the thermoplastic composite can be bound within the framework of a mechanical processing in a firm and permanent manner to a plurality of materials used in the production of shoes.

It was now found that a combination in accordance with the invention of thermoplastic binding agent and a component of natural latex in the processing of the composite material in the hot-cold process ensures the thermal deformability as well as a necessary stability against cold of the composite material.

It was now found in particular that a thermoplastic composite material with the desired properties can be obtained that contains organic fibers, especially leather fibers, and natural latex and the thermoplastic binding agent as matrix material if a thermoplastic binding agent is used as matrix material in addition to at least 2 wt % natural latex to at least 8 wt %, which consists of polymers selected from the group consisting of polyurethanes, polyolefins, polyvinylesters, polyethers, polystyrenes, styrene olefin copolymers, polyacrylates, vinylacetate polymers or ethylene vinylacetate copolymers or mixtures or copolymers of two or more of the cited polymers.

It was found in particular that the use of natural latex in the matrix material of the thermoplastic composite material according to the invention positively influences the above-cited properties of base- and permanent elasticity as well as the resistance to becoming brittle when cold.

The thermoplastic composite material obtainable from the cited polymers preferably has a flow transition boundary of approximately 70 to approximately 100° C.

When indications of content are given for the components of the thermoplastic composite material in weight percents (wt %) in conjunction with the present invention these indications always refer, in as far as nothing else is noted, to the total weight of the thermoplastic composite material.

The subject matter of the invention is therefore a thermoplastic composite material containing

-   -   a) At least 15 wt % of an organic fiber material or of a mixture         of two or more organic fiber materials as component A, and     -   b) At least 10 wt % of a component B consisting of at least 8 wt         % of a thermoplastic binding agent as well as of at least 2 wt %         natural latex,         wherein the thermoplastic binding agent consists of polymers         selected from the group consisting of polyurethanes,         polyolefins, polyvinylesters, polyethers, polystyrenes, styrene         olefin copolymers, polyacrylates, vinylacetate polymers or         ethylene vinylacetate copolymers, or mixtures or copolymers of         two or more of the cited polymers.

Any desired organic fiber material is suitable as component A of the thermoplastic composite material that imparts to the thermoplastic composite material the properties desired by the user, e.g., a certain appearance or certain grip. The term organic fiber material denotes in the sense of the present invention both naturally obtained or naturally obtainable fibers as well as synthetically produced fibers as long as they are based on an “organic basis”. Therefore, fibers such as, e.g., asbestos, glass fibers or carbon fibers are not organic fiber material.

Furthermore, no distinction is made in the context of the previous text between materials that occur in nature already in a fibrous state and those that must first be converted into a fibrous structure by a certain treatment step. Likewise, vegetable as well as animal organic fiber materials are suitable among the natural materials in the sense of the invention.

Plastic fibers, vegetable fibers or animal fibers are normally used in the context of the present invention.

The suitable natural fibers include, e.g., animal fibers such as wool, hairs or silk. Vegetable fibers can also be used, e.g., cotton, kapok, flax, hemp, jute, kenaf, ramie, broom, manila, coconut or sisal. Suitable plastic fibers of natural polymers are cupro fibers, viscose fibers, modal fibers, acetate fibers, triacetate fibers as well as protein fibers or alginate fibers or mixtures of two or more of the cited fibers.

Suitable fibers of synthetic polymers are, e.g., polyacrylic fibers, polymethacrylic fibers, polyvinylchloride fibers, fluorine-containing polymeric fibers, polyethylene fibers, polypropylene fibers, vinylacetate fibers, polyacrylonitrile fibers, polyamide fibers, polyester fibers or polyurethane fibers.

However, it is especially preferable to use leather fibers as organic fiber material. In order to obtain these fibers, leather remnants are comminuted with a suitable process and defibered so that the fibers obtained can be subsequently used within the context of the process according to the invention to obtain a thermoplastic composite material with leather-like properties.

Leather fibers can basically be obtained from any type of leather remnants. They can be chromium-tanned, vegetable-tanned or aldehyde-tanned leathers or their pre-products such as, e.g., shavings or split leather. Leather types that can be used within the context of the invention are, e.g., upper leather, velour leather, crust leather, lower leather, lining leather, sleek leather as well as technical leather.

The organic fiber material is comminuted to a stretched length of approximately 0.1 to 20 mm as a function of the desired decorative or mechanical effect. A length of approximately 0.5 to 20 mm, preferably approximately 1 to approximately 10 mm and especially preferably approximately 3 to approximately 8 mm fiber length is suitable in particular when using leather fibers. The fiber length is measured in the stretched state of the fiber. It can of course occur, depending on the initial material and the type of comminution, that the fiber assumes an irregularly curved form without external influence.

Component A is contained in the thermoplastic composite material according to the invention in an amount of at least approximately 15 wt % as base material. As the portion of A rises, the thermoplastic composite material increasingly assumes the properties of the organic fiber material. It can therefore be advantageous, depending on the desired effect, to use, e.g., at least 20 wt % or at least approximately 25 wt % of component A in the thermoplastic composite material according to the invention. However, the portion of the organic fiber material can also optionally be greater, e.g., approximately 30 wt %, 35 wt %, 40 wt %, 45 wt %, 50 wt %, 55 wt % or even more than approximately 60 wt %, portion of e.g., 65 wt % or even 70 wt % and more being possible. The portion of fiber materials is especially preferably approximately 25 to approximately 65 wt % and quite especially preferably approximately 35 to approximately 55 wt %.

Leather fibers are preferably contained in the thermoplastic composite material according to the invention as component A.

In order to provide the thermoplastic composite material with the thermoplastic properties required for further processing, the thermoplastic composite material contains a thermoplastic binding agent as component B in addition to natural latex.

The term “thermoplastic binding agent” denotes in the context of the present text polymeric compounds that serve as matrix in the composite material in addition to the natural latex used. As a rule, polymeric materials with a molecular weight greater than approximately 1000 are used as thermoplastic binding agent but the molecular weight is preferably greater.

The molecular weight (M_(n)) of the polymers present in the binding agent is preferably between approximately 10,000 and approximately 1,000,000, especially preferably between approximately 20,000 and approximately 300,000 and in particular preferably between approximately 50,000 and approximately 150,000.

The term “thermoplastic binding agent” stands in the context of the present text for the totality of the thermoplastically reacting, polymeric matrix material, that is of that matrix component that constitutes, in addition to the natural latex, component B of the composite material independently of how many polymeric components it consists of and how many preparations containing the polymer(s) constituting the thermoplastic binding agent(s) were required for its production.

The distribution of the molecular weight of the polymers as it can be determined, e.g., by gel permeation chromatography (GPC) does not have to be monomodal. The thermoplastic binding agent can optionally also have a bi- or higher modal distribution.

In order to produce the thermoplastic composite material according to the invention at least 8 wt % of a thermoplastic binding agent consisting of polymers is used, selected from polyurethanes, polyolefins, polyvinylesters, polyethers, polystyrenes, styrene olefin copolymers, polyacrylates, vinylacetate polymers or ethylene vinyl acetate copolymers or mixtures or copolymers of two or more of the cited polymers.

In a preferred embodiment of the invention thermoplastic binding agents containing at least two different polymers are used to produce the thermoplastic composite materials for component B. The term “two different polymers” denotes in the context of the present invention two polymer types that differ in their chemical composition, that is, in the type of monomers participating in the structure of the polymers, or, if two or more monomers participated in the structure of the polymer, in the ratio of the monomers to one another, or in both. It is immaterial whether the individual polymer has thermoplastic properties as long as the mixture of two different polymers has an appropriate thermoplasticity.

In the context of the present invention all polymers with at least two urethane groups in the polymer backbone are to be considered as polyurethanes. In the context of the present invention all thermoplastic polyurethanes known to those skilled in the art in the area of polyurethane chemistry are suitable as polyurethanes, in particular polyurethanes like those customarily used in the context of producing thermoplastic formed pieces, in particular from foils, or for the thermoplastic coating of surfaces. For example, polyesterpolyurethanes or polyetherpolyurethanes like those obtainable by reacting dicarboxylic acids with appropriate polyfunctional alcohols, especially difunctional alcohols, e.g., difunctional polyethers such as polyethylene oxide to polyether- or polyester polyols and subsequently reacting the appropriate polyether- or polyester polyols with di- or polyfunctional isocyanates are suitable.

Polyolefins suitable in the context of the present invention are obtainable, e.g., by radical or coordinative polymerization of α-olefins, especially of ethylene or propylene.

In particular, the polymers of vinylacetate are suitable as polyvinylesters in the context of the present invention.

Polyethers suitable in the context of the present invention are, e.g., polyethylene oxide, polypropylene oxide, polybutylene oxide or polytetrahydrofuran, especially with a molecular weight of more than approximately 5,000.

Suitable polystyrenes are, e.g., the polymers of styrene or α-methylstyrene.

The styrene olefin copolymers like those obtainable by copolymerization of styrene with mono- or diolefins, especially butadiene, are also suitable as polymers for use in the thermoplastic binding agent of the thermoplastic composite material according to the invention.

Suitable polyvinylesters are the polymerizates of the esters of unsaturated alcohols with appropriate carboxylic acids. Suitable unsaturated alcohols are, e.g., the unsaturated, aliphatic alcohols with 2 to approximately 22 C-atoms, especially with 2 to approximately 8 C-atoms. Suitable carboxylic acids are the linear and branched alkane acids with 2 to approximately 22 C-atoms, especially with 2 to approximately 8 C-atoms.

Polymers that are present in the form of an aqueous dispersion are preferably use for the production of composite substances according to the invention. They can be anionically stabilized or cationically stabilized polymer dispersions. The stabilization of the dispersion can be effected, e.g., by self-emulsifiable polymers, that is, by polymers carrying appropriate hydrophilic groups, e.g., carboxylic acid groups or amino groups. However, dispersions can also be used whose stability is affected by suitable anionic or cationic dispersants or emulsifiers.

The terms “polyacrylate” or “polyacrylates” as they are used in the context of the present text refer in the following to polymers or copolymers of acrylic acid and/or its derivatives as well as to polymers or copolymers of methacrylic acid and/or its derivatives.

Polyacrylates can be produced in that acrylic acid and/or methacrylic acid and/or derivatives of acrylic acid and/or methacrylic acid, e.g., their esters, are polymerized either radically or ionically with mono-or polyfunctional alcohols alone or as a mixture of two or more of them in a known manner. In the context of the present invention, the polyacrylates in anionic dispersion like those obtainable, e.g., by emulsion polymerization of the appropriate monomers and comonomers are preferred. Aqueous anionic dispersions contain as a rule, e.g., the sodium salts, potassium salts and/or ammonium salts of long-chain, aliphatic carboxylic acids and/or sulfonic acids for emulsification. However, alkali-C₁₀₋₁₈-alkyl sulfates, ethoxylated and sulfated and/or sulfonated long-chain, aliphatic alcohols or alkyl phenols as well as sulfodicarboxylic acid esters are also suitable.

Homopolymers or copolymers containing styrene, acrylonitrile, vinylacetate, vinylpropionate, vinyl chloride, vinylidene chloride and/or butadiene in addition to the acrylic acid esters (acrylates) can be used as polyacrylates in the context of the present invention.

In particular, methacrylate, ethylacrylate, n-butylacrylate, isobutylacrylate, tert.-butylacrylate, hexylacrylate, 2-ethylhexylacrylate or laurylacrylate can be considered as monomers in the production of polyacrylates. Optionally, acrylic acid, methacrylic acid, acrylamide or methacrylamide can also be added as further monomers in slight amounts during the polymerization.

Even other acrylates and/or methacrylates with one or more functional groups can optionally also be present in the polymerization. They are, e.g., maleic acid, itaconic acid, butanediol diacrylate, hexanediol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, 2-hydroxyethylacrylate, 2-hydroxymethylmethacrylate, hydroxypropylacrylate, propyleneglycolmethacrylate, butanediol monoacrylate, ethyldiglycolacrylate as well as a monomer carrying sulfonic acid, e.g., 2-acrylamido-2-methylpropane sulfonic acid.

If data about the content of natural latex in the thermoplastic composite materials is presented in weight percents (wt %) in the context of the present invention, this data refers to the weight proportions of the natural latex polymer in the ready composite material.

In the framework of a preferred embodiment of the present invention, the thermoplastic binding agent used in component B contains at least one of the above-cited polymers, the portion of the thermoplastic binding agent in the entire composite substance being at least approximately 8 wt %, e.g., at least approximately 10 wt %, at least approximately 20 wt %, at least approximately 30 wt % or at least approximately 40 wt % or more, e.g., at least approximately 50 to approximately 70 wt % or up to approximately 80 wt %.

In a preferred embodiment of the invention, the portion of thermoplastic binding agent contains at least one polymer selected from the group consisting of styrene olefin copolymers, vinylacetate polymers or ethylene vinylacetate copolymers or mixtures or copolymers of two or more of the cited polymers.

It furthermore turned out that the thermoplastic properties of the thermoplastic composite material according to the invention can be influenced by the selection of polymers for the thermoplastic binding agent, selected from the group consisting of styrene olefin copolymers, vinylacetate polymers or ethylene vinylacetate copolymers or mixtures or copolymers of two or more of the cited polymers with a suitable minimum film-formation temperature. The minimum film-formation temperature of a polymer is the lowest temperature at which a dispersion is just able to form a cohesive film after evaporation of the water. It is close to the glass transition temperature T_(g) of the polymer and determines with the film formation one of the most important application technology properties of a polymer dispersion. The minimum film formation temperature (MFT) is determined as a rule according to DIN 53787. A metal plate to which a temperature gradient is applied serves as measuring apparatus. At which temperature the film begins to become cracked or where the so-called white point is located at which the opaque film begins to become clear is observed.

At least one of the polymers has an MFT of at least 20° C. in the framework of a preferred embodiment of the present invention.

In the framework of another preferred embodiment of the present invention at least one of the polymers has an MFT of approximately 25° C. to approximately 35° C.

The entire portion of component B in the thermoplastic composite material is preferably at least approximately 10 wt %. It can be advantageous, e.g., for a well-directed change of property, if the thermoplastic composite material contains at least 20 wt % or at least approximately 30 wt % or more of component B, e.g., at least approximately 40 to at least approximately 50 wt %. In a preferred embodiment of the invention the portion of component B in the entire thermoplastic composite material is approximately 25 to approximately 40 wt %.

In addition to the organic fiber material as component A and the thermoplastic binding agent as component B, the thermoplastic composite material according to the invention can also contain further components, preferably in a portion up to approximately 20 wt %. This includes, e.g., inorganic salts, preservative agents, dyes, natural and/or synthetic fats, paraffins, natural and/or synthetic oils, silicone oils as well as ionic and/or non-ionic surfactants.

Salts of aluminum or of copper are preferably used as inorganic salts and aluminum sulfate is especially preferred.

The inorganic salts are used as a rule in the context of the production process, that will be described in the further course of the present text, for precipitating (coagulating) the polymeric binding agent. As a rule, the largest portion of the metal salt is removed with the aqueous phase from the composite but a small remnant can remain in the composite material.

Among the preservative agents, those preservative agents are especially preferred that have a fungicidal spectrum of action. The preservative agent Preventol® A11D distributed by the BAYER company, Leverkusen, is well-suited in the sense of the invention.

In a preferred embodiment of the invention, component B contains up to 70 wt % (relative to the total weight of component B) polymer, selected from the group consisting of styrene olefin copolymers, vinylacetate polymers or ethylene vinylacetate copolymers or mixtures or copolymers of two or more of the cited polymers.

In a further preferred embodiment the thermoplastic composite material contains

-   -   approximately 25 to approximately 65 wt % organic fibers,     -   approximately 2 to approximately 30 wt % natural latex,     -   approximately 8 to approximately 35 wt % polymers, selected from         the group consisting of styrene olefin copolymers, vinylacetate         polymers or ethylene vinylacetate copolymers or mixtures or         copolymers of two or more of the cited polymers,     -   optionally up to 20 wt % inorganic salts, preservative agents,         dyes, natural and/or synthetic fats, paraffins, natural and/or         synthetic oils,. silicone oils, ionic and/or non-ionic         surfactants.

In an especially preferred embodiment the thermoplastic composite material contains

-   -   approximately 35 to approximately 55 wt % organic fibers,     -   approximately 10 to approximately 25 wt % natural latex,     -   approximately 10 to approximately 30 wt % polymers, selected         from the group consisting of styrene olefin copolymers,         vinylacetate polymers or ethylene vinylacetate copolymers or         mixtures or copolymers of two or more of the cited polymers,     -   optionally up to 20 wt % inorganic salts, preservative agents,         dyes, natural and/or synthetic fats, paraffins, natural and/or         synthetic oils, silicone oils, ionic and/or non-ionic         surfactants.

The thermoplastic composite material according to the invention should preferably serve for shoe components such as heel caps, toe caps, outer soles and especially preferably for manufacturing heel caps in the shoe industry and have the rational processing properties of high-quality synthetic heel cap material in addition to the desired leather-like properties of high-quality LEFA heel cap materials.

In a preferred embodiment of the invention, the thermoplastic composite material has a flow transition range of approximately 70° C. to 100° C.

At temperatures within the indicated flow transition range, the thermoplastic composite material according to the invention can be subjected to changes of form, e.g., moldings with precise contours that retain a stable form after dropping below the flow transition range. The thermoplastic composite material according to the invention has high tear resistance and elasticity in this case. The processing can take place in a more rational manner than with synthetic cap material on account of the material properties.

The production of the thermoplastic composite material according to the invention preferably takes place by bringing component A in contact with the components of component B, these components being preferably present in aqueous dispersion.

Since component B has more than one component, that is, more than one polymer, both polymers can be present in a dispersion at the same time. However, it is just as possible in the context of the present invention that both polymers are present in different dispersions.

Components A and the components of component B are mixed in one or more dispersions in the context of the production process according to the invention and the components of component B are coagulated at the same time, that is, during the mixing, or subsequently, that is, in their own process stage after the mixing.

The invention therefore also has as subject matter a process for producing a thermoplastic composite material containing

-   -   a) at least 15 wt % of an organic fiber material or of a mixture         of two or more organic fiber materials as component A         and     -   b) at least 10 wt % of a component B consisting of at least 8 wt         % of a thermoplastic binding agent and at least 2 wt % natural         latex,         in which fibers with a stretched fiber length of 0.1 to 20 mm         are mixed as component A simultaneously or in any successive         sequence with a polymer dispersion or a mixture of two or more         polymer dispersions selected from the group consisting of         natural latex, polyurethanes, polyolefins, polyvinylesters,         polyethers, polystyrenes, styrene olefin copolymers,         polyacrylates, vinylacetate polymers or ethylene vinylacetate         copolymers, or mixtures or copolymers of two or more of the         cited polymers to form a mixture so that the polymers contained         in the dispersion or the dispersions form component B, and the         mixture is subsequently treated with an aqueous solution of an         aluminum salt or copper salt, dewatered and dried.

If two or more different polymer dispersions are used, e.g., differently stabilized dispersions can be used in the context of the present invention. For example, when two polymer dispersions are used, an anionically stabilized dispersion and a cationically stabilized dispersion can be used. The dispersions can be selected in such a manner that a substantially complete coagulation, that is, a substantially complete precipitation of the binding agent contained in the dispersion takes place. However, it is just as possible to proceed in such a manner that only a part of the binding agent is precipitated.

However, in a preferred embodiment according to the invention, polymer dispersions are used that are substantially identically stabilized, at least as regards the charge of the stabilizing species. For example, dispersions can be used that are anionically or cationically stabilized. In a further preferred embodiment according to the invention, anionically stabilized polymer dispersions are used.

The treatment of the mixture with an aqueous solution of an aluminum salt or copper salt takes place in such a manner that following the treatment substantially all polymer molecules present in the mixture are precipitated, that is, coagulated.

The following exemplary process description serves solely to illustrate a possibility for carrying out the process according to the invention and is not limited thereto. Deviations from the following process operating sequence, optionally with optimization of the subsequently described process, can be performed without problems by those skilled in the art depending of the situation in front of him.

For producing the thermoplastic composite materials according to the invention, tanned leather remnants are comminuted (pre-cut) in knife mills to a size of approximately 1 cm² in area. The comminution takes place dry as a rule in this stage.

The leather remnants pre-comminuted in this manner are weighed and defibered wet by so-called disk refiners. The addition of water is controlled in such a manner that a node-free fiber pulp is obtained consisting of approximately 5 wt % fibers and approximately 95 wt % water (corresponding to approximately 1000 kg fibers to 20 m³ water). The comminution is preferably carried out in such a manner that a part of the wastewater that is standing later in the process is returned at this location into the circuit. Proportions of wastewater of approximately 50% and preferably above can be achieved from the total water used during the comminution process.

The suspension of leather fibers in water obtainable in this manner is subsequently transferred into a suitable vessel, preferably a preparation vat. The transferred amount is measured in such a manner that the concentration of leather fibers is between approximately 1.5 and approximately 2.5 wt % relative to the total batch amount provided.

If the leather fibers contain a high proportion of chrome-tanned leather or if the leather fibers consist exclusively of chrome-tanned leather, at first vegetable tanning substances, e.g., chestnut wood extract, quebracho, mimosa or valonia are added.

Subsequently, fatting agents are added. All leather fatting agents emulsifiable in water are suitable as fatting agents.

In addition, dyes can be added to the batch. This usually involves quantitatively attaching iron oxide dyes.

Moreover, the batch can be compounded with preservative agents, natural and/or synthetic fats, natural and/or synthetic oils, silicone oils and/or ionic and/or non-ionic surfactants.

The polymer dispersion or the mixture of two or more different polymer dispersions is subsequently added.

If two or more different polymer dispersions are to be used, they can be added either at the same time or successively in any desired sequence to the mixture.

If two polymer dispersions with different stabilization, that is, different charge of the stabilizing species are added to the mixture, the anionically stabilized polymer dispersion or the anionically stabilized polymer dispersions is/are added separately from the cationically stabilized polymer dispersion or the cationically stabilized dispersions. The sequence is not relevant here.

After the end of the addition of the polymer dispersions the mixture is compounded with a solution of an aluminum salt or copper salt. Aluminum sulfate is preferably used and approximately 40 to 300 1, preferably approximately 100 to approximately 250 1, and especially preferably approximately 120 to approximately 200 1 of an approximately 20 to preferably 60 wt % aluminum sulfate solution are added per 100 kg batch.

After approximately one hour agitation the batch is freed of excess water with the aid of a suitable dewatering device. For this, on the one hand dewatering equipments are available that operate in the so-called batch process, e.g., a so miller press; however, a continuous processing of a long-sieve dewatering machine is preferred. The batch is dewatered on the long-sieve watering machine to a residual water content of approximately 70 wt %.

Following the dewatering procedure the material obtained is dewatered mechanically to a residual water content of approximately 50 wt % with the aid of a suitable press device.

The material treated in this manner is now conducted through a suitable thermal drying equipment where it is dried to a residual water content of approximately 10 wt % and subsequently wound onto rollers. It is also possible, depending on the application striven for, to dry the material to lower residual water contents.

Depending on the intended processing in the shoe industry, the material can subsequently be further refined (grinding, calendering, trimming) and cut into plates or rolls.

The composite substance obtained in this manner has, e.g., a flow transition range of approximately 70° C. to approximately 100° C.

In a further preferred embodiment according to the invention, the composite material is provided with a thermally activatable adhesive in order to achieve a durable fastening of the composite material with lining and upper material in a rational process when used as heel cap material or toe cap material. During the processing, the thermal activation of the adhesive takes place in the flow transition range of the composite substance.

In the sense of the present invention adhesives are non-metallic, preferably organic substances that bind the joint parts by surface attachment and inner strength. Adhesives include, e.g., glues, dispersion adhesives, solvent-containing adhesives, hot-melt adhesives and/or contact adhesives.

Organic adhesives are preferably used in the context of the present invention that can be either physically hardening adhesives or chemically reacting adhesives or a combination of both. The physically hardening adhesives that can be used in the sense of the present invention include, e.g., adhesives present in solution or dispersion, contact adhesives or hot-melt adhesives. For example, those adhesives that impart a sufficient adhesion to the surfaces to be adhered without spitting off volatile components can be used as chemically reacting adhesives. However, adhesives can also be used that achieve the required adhesion while splitting off volatile components. The adhesives can be cold-hardening as well as also hot-hardening, exhibit a thermoplastic, duromer or elastomeric final state and be used in a single-component, two-component or multicomponent manner.

Hot-melt adhesives whose softening point is approximately 60° C. to approximately 120° C. are used in one embodiment. In a special embodiment hot-melt adhesives are used whose softening point is approximately 80° C. to approximately 100° C. In a quite special embodiment hot-melt adhesives are used whose softening point is approximately 80° C. to approximately 100° C. and the adhesive is based on polyesters, polyamides or polycarbonates.

The adhesive is applied onto the thermoplastic composite material in a hot process, e.g., by extruder application with slit nozzle or rollercoater application. The adhesive can also be applied by powder application and be subsequently sintered on thermally. These processes are cold-hardening processes.

In one embodiment hot-melt adhesives are applied by extruder slit-nozzle application between approximately 50 to approximately 100 g/m². In another embodiment hot-melt adhesive powder coatings are applied between approximately 30 to approximately 80 g/m². In a special embodiment hot-melt adhesive powder coatings are applied between approximately 40 to approximately 70 g/m².

The thermoplastic composite materials according to the invention are suitable for numerous other applications in addition to the manufacture of thermally formable shoe components, e.g., for coating the surface of objects such as, e.g., furniture fronts with or without inner radii, for the surface coating of parts in the inner spaces of motor-driven automobiles, or for jacketing the profile of wall-, floor- and ceiling panels. 

1. A thermoplastic composite material containing: a) at least 15 wt % of an organic fiber material or of a mixture of two or more organic fiber materials as component A; and b) at least 10 wt % of a component B consisting of at least 8 wt % of a thermoplastic binding agent as well as of at least 2 wt % natural latex; wherein the thermoplastic binding agent consisting of polymers selected from the group consisting of polyurethanes, polyolefins, polyvinylesters, polyethers, polystyrenes, styrene olefin copolymers, polyacrylates, vinylacetate polymers or ethylene vinylacetate copolymers, or mixtures or copolymers of two or more of the cited polymers.
 2. The composite material according to claim 1, comprising 25 to 65 wt % organic the fiber material as component A.
 3. The composite material according to claim 1, comprising 2 to 30 wt % natural latex and 8 to 70 wt % thermoplastic binding agent as component B, the total portion of component B in the composite material being a maximum of 85 wt %.
 4. The composite material according to claim 1, wherein the thermoplastic binding agent comprises at least 8 wt % of at least one polymer selected from the group consisting of styrene olefin copolymers, vinylacetate polymers or ethylene vinylacetate copolymers, or mixtures or copolymers of two or more of the cited polymers.
 5. The composite material according to claim 1, characterized in that the thermoplastic binding agent contains at least 8 to 30 wt % of at least one polymer selected from the group consisting of styrene olefin copolymers, vinylacetate polymers or ethylene vinylacetate copolymers, or mixtures or copolymers of two or more of the cited polymers.
 6. The composite material according to claim 1, characterized in that the thermoplastic binding agent contains at least one polymer with a minimum film-formation temperature (MFT) of at least 20° C.
 7. The composite material according to claim 1, characterized in that the composite material has a flow transition boundary in the range from approximately 70° C. to approximately 100° C.
 8. The composite material according to claim 1, characterized in that it optionally contains, in addition to components A and B, up to 20 wt % of one or more components selected from the group consisting of inorganic salts, preservative agents, dyes, natural and/or synthetic fats, paraffins, natural and/or synthetic oils, silicone oils as well as ionic and/or non-ionic surfactants.
 9. The composite material according to claim 1, characterized in that plastic fibers, vegetable fibers or animal fibers are contained as component A.
 10. The composite material according to claim 1, characterized in that leather fibers are contained as component A.
 11. The composite material according to claim 1, characterized in that the fibers of component A have a stretched length of approximately 0 1 to approximately 20 mm.
 12. The composite material according to claim 1, characterized in that the material is provided with a thermally activatable adhesive, preferably a hot-melt adhesive.
 13. A process for producing a thermoplastic composite material containing: a) at least 15 wt % of an organic fiber material or of a mixture of two or more organic fiber materials as component A; and b) at least 10 wt % of a component B consisting of at least 2 wt % natural latex with at least 8 wt % of a thermoplastic binding agent; in which fibers with a stretched fiber length of 0.1 to 20 mm are mixed as component A simultaneously or in any successive sequence with a polymer dispersion or a mixture of two or more polymer dispersions selected from the group consisting of natural latex, polyurethanes, polyolefins, polyvinylesters, polyethers, polystyrenes, styrene olefin copolymers, polyacrylates, vinylacetate polymers or ethylene vinylacetate copolymers, or mixtures or copolymers of two or more of the cited polymers to form a mixture so that the polymers contained in the dispersion or the dispersions form component B, and the mixture is subsequently treated with an aqueous solution of an aluminum salt or copper salt, dewatered and dried.
 14. The use of a thermoplastic composite material according to claim 1 for producing thermally formable shoe components such as heel caps and toe caps.
 15. The use of a thermoplastic composite material produced according to claim 13 for producing thermally formable shoe components such as heel caps and toe caps.
 16. The use of a thermoplastic composite material according to claim 1 for jacketing the profile of wall-, floor and ceiling panels, for coating the surface of furniture fronts with or without inner radii, for edge gluing, and for the surface coating of parts in the inner spaces of motor-driven automobiles.
 17. The use of a thermoplastic composite material according to claim 13 for jacketing the profile of wall-, floor and ceiling panels, for coating the surface of furniture fronts with or without inner radii, for edge gluing, and for the surface coating of parts in the inner spaces of motor-driven automobiles. 